Dual temperature heater

ABSTRACT

A method and apparatus for heating a substrate in a chamber are provided. an apparatus for positioning a substrate in a processing chamber. In one embodiment, the apparatus comprises a substrate support assembly having a support surface adapted to receive the substrate and a plurality of centering fingers for supporting the substrate at a distance parallel to the support surface and for centering the substrate relative to a reference axis substantially perpendicular to the support surface. The plurality of the centering fingers are movably disposed along a periphery of the support surface, and each of the plurality of centering fingers comprises a first end portion for either contacting or supporting a peripheral edge of the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 14/875,392, filed Oct. 5, 2015, which is a continuation of U.S.patent application Ser. No. 12/851,794, filed Aug. 6, 2010, which claimsbenefit of U.S. provisional patent application Ser. No. 61/232,172,filed Aug. 7, 2009, all of which are herein incorporated by reference intheir entirety.

BACKGROUND Field

Embodiments of the present invention generally relate to apparatus andmethods for processing semiconductor substrates. More particularly,embodiments of the present invention relate to an apparatus and methodsfor heating a substrate in a chamber.

Description of the Related Art

The effectiveness of a substrate fabrication process is often measuredby two related and important factors, which are device yield and thecost of ownership (CoO). These factors are important since they directlyaffect the cost to produce an electronic device and thus a devicemanufacturer's competitiveness in the market place. The CoO, whileaffected by a number of factors, is greatly affected by the system andchamber throughput, or simply the number of substrates per hourprocessed using a desired processing sequence.

During certain substrate processing sequences, such as, for example,chemical vapor deposition processes (CVD) or plasma enhanced chemicalvapor deposition processes (PECVD), it may be desirable to pre-treat asubstrate prior to performing a deposition process. In certainpre-treatment processes, the substrate may be heated, for example, usingan anneal process, to a first temperature prior to the depositionprocess. During the deposition process, the substrate is heated to asecond temperature different from the first temperature. For manydeposition processes, the substrate is placed on a substrate supportcomprising a heater. This heater is used to heat the substrate to boththe first temperature and the second temperature. When there is somevariance between the first temperature and the second temperature, forexample, when the second temperature is higher than the firsttemperature, there is a delay between the pre-treatment process and thedeposition process so that the temperature of the heater may beincreased from the first temperature to the second temperature. Thisdelay leads to an overall increase in substrate processing time and acorresponding decrease in device yield.

Therefore, there is a need for an apparatus and process that canposition and heat a substrate in a processing chamber in acost-effective and accurate manner.

SUMMARY

Embodiments of the present invention generally relate to apparatus andmethods for processing semiconductor substrates. More particularly,embodiments of the present invention relate to an apparatus and methodsfor heating a substrate in a chamber. In one embodiment, an apparatusfor positioning a substrate in a processing chamber is provided. Theapparatus comprises a substrate support assembly having a supportsurface adapted to receive the substrate and a plurality of centeringfingers for supporting the substrate at a distance parallel to thesupport surface and for centering the substrate relative to a referenceaxis substantially perpendicular to the support surface. The pluralityof centering fingers are movably disposed along a periphery of thesupport surface, and each of the plurality of centering fingerscomprises a first end portion for either contacting or supporting aperipheral edge of the substrate, the first end portion comprising anupper end portion extending above the support surface of the substratesupport for releasably contacting the peripheral edge of the substrate,a support tab positioned on the upper end portion, and a substratesupport notch formed by an intersection of the support tab and the upperend portion, for supporting the substrate. The first end portion ismovable between a first position and a second position. Movement fromthe first position to the second position causes the centering finger torelease the peripheral edge of the substrate and movement from thesecond position to the first position causes the centering finger topush the substrate in a direction toward the reference axis or positionsthe centering fingers for supporting the substrate.

In another embodiment a method for centering a substrate in a processingchamber is provided. A substrate support having an embedded heater and aheated support surface adapted to receive a substrate is provided. Aplurality of centering fingers disposed along a circle centered at areference axis substantially perpendicular to the support surface isprovided. Each centering finger comprises an end portion configured tocontact a peripheral edge of the substrate, and the end portion isradially movable towards and away from the reference axis. A support tabis positioned on the end portion and a substrate support notch is formedat an intersection of the support tab and the end portion, forsupporting the substrate at a distance from the support surface of thesubstrate support. The substrate is positioned on the support tabs ofeach of the plurality of centering fingers. A pre-treatment process isperformed on the substrate at a first processing temperature of thesubstrate. The substrate is removed from the support tabs. The endportion of each centering finger is moved radially outward and away fromthe reference axis. The substrate is placed on the substrate support,wherein the substrate and the centering fingers do not contact. The endportion of each centering finger is moved radially inwards to contact aperipheral edge of the substrate for centering the substrate. Thesubstrate is positioned with the end portions of the centering fingers.A deposition process is performed on the substrate at a secondprocessing temperature of the substrate, wherein the first processingtemperature is different from the second processing temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic cross-sectional view of one embodiment of a PECVDsystem according to embodiments described herein;

FIG. 2A is a partially enlarged cross-sectional view of one embodimentof a centering finger of FIG. 1 in a supporting position;

FIG. 2B is a partially enlarged cross-sectional view of one embodimentof a centering finger of FIG. 1 in a centering position;

FIG. 2C is a partially enlarged cross-sectional view of one embodimentof a centering finger of FIG. 1 in a disengaging position;

FIG. 3A is a simplified overhead view of one embodiment of a centeringmechanism using three centering fingers to support a substrate;

FIG. 3B is a simplified overhead view of one embodiment of a centeringmechanism using three centering fingers to center a substrate;

FIG. 4 is a cross-sectional view showing one embodiment of a centeringfinger having an eccentric weighed portion;

FIG. 5A is a partial cross-sectional view illustrating one embodiment ofa centering finger in a supporting position;

FIG. 5B is a partial cross-sectional view illustrating one embodiment ofa centering finger in a centering position;

FIG. 5C is a partial cross-sectional view illustrating one embodiment ofa centering finger in a disengaging position;

FIG. 6 is a partial cross-sectional view illustrating one embodiment ofa centering finger; and

FIG. 7 is a partial cross-sectional view illustrating one embodiment ofa centering finger.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

Embodiments described herein relate to an apparatus and method forheating and centering a substrate that are applicable for variouschamber systems configured to apply diverse semiconductor processes on asubstrate. Although the embodiments are exemplarily described for use ina deposition chamber, some embodiments may be applicable for other typesof process chambers that necessitate heating and centering of asubstrate. Examples include, without limitations, loadlock chambers,testing chambers, deposition chambers, etching chambers, and thermaltreatment chambers.

FIG. 1 is a schematic cross-sectional view of one embodiment of a PECVDsystem 100 having a centering mechanism 140. The system 100 includes aprocess chamber 102 coupled to a gas source 104. The process chamber 102has walls 106 and a bottom 108 that partially define a process volume110. The process volume 110 may be accessed through a port 101 formed inthe walls 106 that facilitate movement of a substrate 112 into and outof the process chamber 102. The walls 106 and bottom 108 may befabricated from a unitary block of aluminum or other material compatiblewith processing. The walls 106 support a lid assembly 114. The processchamber 102 may be evacuated by a vacuum pump 116.

A temperature controlled substrate support assembly 120 may be centrallydisposed within the process chamber 102. The substrate support assembly120 may support a substrate 112 during processing. In one embodiment,the substrate support assembly 120 comprises a support base 122 made ofaluminum that may encapsulate at least one embedded heater 103 operableto controllably heat the substrate support assembly 120 and thesubstrate 112 positioned thereon to a predetermined temperature. In oneembodiment, the substrate support assembly 120 may operate to maintainthe substrate 112 at a temperature between about 150 degrees Celsius (°C.) to about 1,000 degrees Celsius (° C.), depending on the depositionprocessing parameters for the material being deposited. In oneembodiment, the substrate support assembly may operate to maintain thesubstrate 112 at a temperature between about 250 degrees Celsius (° C.)to about 270 degrees Celsius (° C.), during a pre-treatment process suchas an anneal process. In one embodiment, the substrate support assemblymay operate to maintain the substrate 112 at a temperature between about350 degrees Celsius (° C.) to about 400 degrees Celsius (° C.), during adeposition process.

The substrate support assembly 120 may have an upper support surface 124and a lower surface 126. The upper support surface 124 supports thesubstrate 112. The lower surface 126 may have a stem 128 coupledthereto. The stem 128 couples the substrate support assembly 120 to alift system 131 that moves the substrate support assembly 120 verticallybetween an elevated processing position and a lowered position thatfacilitates substrate transfer to and from the process chamber 102. Thestem 128 additionally provides a conduit for purge gas and electricaland temperature monitoring leads between the substrate support assembly120 and other components of the system 100. A bellows 130 may be coupledbetween the stem 128 and the bottom 108 of the process chamber 102. Thebellows 130 provides a vacuum seal between the process volume 110 andthe atmosphere outside the process chamber 102 while facilitatingvertical movement of the substrate support assembly 120.

To facilitate the transfer of the substrate 112, the support base 122also includes a plurality of openings 133 through which lift pins 132are movably mounted. The lift pins 132 are operable to move between afirst position and a second position. The first position, shown in FIG.1, allows the substrate 112 to rest on the upper support surface 124 ofthe support base 122. The second position (not shown) lifts thesubstrate 112 above the support base 122 so that the substrate 112 canbe transferred to a substrate handling robot coming through the port101. Upward/downward movements of the lift pins 132 may be driven by amovable plate 134 connected to an actuator 136.

The support base 122 may be electrically grounded such that RF powersupplied by a power source 138 to a gas distribution plate assembly 141positioned between the lid assembly 114 and the support base 122 (orother electrode positioned within or near the lid assembly of thechamber) may excite gases present in the process volume 110 between thesupport base 122 and the gas distribution plate assembly 141. The RFpower from the power source 138 may be selected commensurate with thesize of the substrate 112 to drive the chemical vapor depositionprocess.

The substrate support assembly 120 further comprises a centeringmechanism 140 operable to center the substrate 112 relative to avertical reference axis Z perpendicular to the substrate support planeof the support base 122. The centering mechanism 140 is also operable tosupport the substrate 112 at a distance parallel to a surface of thesupport base 122. The centering mechanism 140 comprises three or moremovable centering fingers 142 positioned at a periphery of the supportbase 122, and an opposing plate 144 placed below the fingers 142. Eachcentering finger 142 is pivotally mounted on the support base 122 via ashaft 146. The opposing plate 144 and the support base 122 arerelatively movable so that the opposing plate 144 may contact and pivotthe fingers 142 in a release position and stay free from the fingers 142in a centering position or supporting position.

In one embodiment, the opposing plate 144 is stationary and the relativemovement between the support base 122 and the opposing plate 144 is dueto the vertical movement of the support base 122. When there is nosubstrate 112 positioned on the support base 122, the fingers 142 engagein a supporting position for supporting the substrate 112 as shown inFIG. 2A. When the substrate 112 is positioned on the support base 122,the fingers 142 engage on the peripheral edge of the substrate 112 tocenter the substrate 112 when the substrate support assembly 120 is inan elevated position as shown in FIG. 1 and FIG. 2B, and disengage fromthe peripheral edge of the substrate 112 when the substrate supportassembly 120 is in a lowered position as shown in FIG. 2C. Furtherdetails of the centering mechanism 140 and its operation will bedescribed hereafter.

The process chamber 102 may additionally comprise a circumscribingshadow frame 150. The shadow frame 150 is positioned to preventdeposition at the edge of the substrate 112, the substrate supportassembly 120, and the centering mechanism 140 to reduce flaking andparticle contamination in the process chamber 102.

The lid assembly 114 provides an upper boundary to the process volume110. The lid assembly 114 may be removed or opened to service theprocess chamber 102. In one embodiment, the lid assembly 114 may befabricated from aluminum.

The lid assembly 114 may include an entry port 160 through which processgases provided by the gas source 104 may be introduced into the processchamber 102. A gas distribution plate assembly 141 may be coupled to aninterior side of the lid assembly 114. The gas distribution plateassembly 141 includes an annular base plate 162 having a blocker plate164 disposed intermediate to a faceplate (or showerhead) 166. Theblocker plate 164 provides an even gas distribution to a backside of thefaceplate 166. The processing gas from the entry port 160 enters a firsthollow volume 168 partially limited between the annular base plate 162and the blocker plate 164, and then flows through a plurality ofpassages 170 formed in the blocker plate 164 into a second volume 172between the blocker plate 164 and the faceplate 166. The processing gasthen enters the process volume 110 from the second volume 172 through aplurality of passages 174 formed in the faceplate 166. The faceplate 166is isolated via an insulator material 176. The annular base plate 162,blocker plate 164 and faceplate 166 may be fabricated from stainlesssteel, aluminum, anodized aluminum, nickel or any other RF conductivematerial.

The power source 138 applies a radio frequency (RF) bias potential tothe annular base plate 162 to facilitate the generation of plasmabetween the faceplate 166 and the support base 122. The power source 138may include a high frequency RF power source (“HFRF power source”)capable of generating an RF power at about 13.56 MHz, or a low frequencyRF power source (“LFRF power source”) generating an RF power at about300 kHz. The LFRF power source provides both low frequency generationand fixed match elements. The HFRF power source is designed for use witha fixed match and regulates the power delivered to the load, eliminatingconcerns about forward and reflected power.

As shown in FIG. 1, a controller 180 may interface with and controlvarious components of the substrate processing system. The controller180 may include a central processing unit (CPU) 182, support circuits184 and a memory 186.

The substrate 112 is transferred to the lift pins 132 in the processchamber 102 by a conveyor that may be a robot or other transfermechanism (not shown), and then placed on the upper support surface 124of the substrate support assembly 120 by moving the lift pins 132downward. As will be discussed below, the centering mechanism 140 thenis operated to center the substrate 112 relative to the reference axisZ.

In one embodiment, one or more temperature sensors 190 are positioned tomonitor the temperature of the backside of the substrate 112. In oneembodiment, the one or more temperature sensors 190, such as a fiberoptic temperature sensor, are coupled to the controller 180 to provide ametric indicative of the temperature profile of the backside of thesubstrate 112. In one embodiment, the data provided by the one or moretemperature sensors 190 may be used in a feedback loop to control thetemperature of the embedded heater 103. In one embodiment, the one ormore temperature sensors are positioned in the support base.

In one embodiment, a purge gas may be provided to the backside of thesubstrate 112 through one or more purge gas inlets 192 connected to apurge gas source 194. The purge gas flown toward the backside of thesubstrate 112 helps prevent particle contamination caused by depositionon the backside of the substrate 112 when the substrate 112 is supportedby the centering mechanism 140. The purge gas may also be used as a formof temperature control to cool the backside of the substrate 112. In oneembodiment, the flow of purge gas may be controlled in response to thedata provided by the one or more temperature sensors 190.

FIG. 2A is a partially enlarged cross-sectional view of one embodimentof a centering finger 142 of FIG. 1 in a supporting position. As shownin FIG. 2A, in the supporting position, the substrate 112 rests on thecentering finger 142. While resting on the centering finger 142, thesubstrate 112 is positioned at a distance “A” from the upper supportsurface 124 of the support base 122. The distance “A” between thesubstrate 112 and the upper support surface 124 of the support base 122is chosen such that the thermal resistance between the substrate 112 andthe embedded heater 103 creates a different temperature on the elevatedsubstrate 112 as compared to when the substrate rests on the uppersupport surface 124 of the support base 122 without having to change thesetpoint temperature of the embedded heater 103. The ability to changethe temperature of the substrate 112 without changing the setpointtemperature of the embedded heater 103 allows for back-to-back processsteps to be performed without the delay of waiting for the heater toeither increase in temperature or decrease in temperature in betweenprocessing steps. Thus leading to an overall decrease in substrateprocessing time and a corresponding increase in device yield.

The centering finger 142 may be made in a single piece, or formed fromthe assembly of multiple component parts. Materials used for thecentering finger 142 may include aluminum nitride, aluminum oxide,ceramics and similar materials or combinations thereof that have a lowcoefficient of thermal expansion and are resistant to the processingenvironment in the process chamber 102. The centering finger 142 ispivotally mounted via the shaft 146 to a joint block 290 protruding fromthe lower surface 126 of the support base 122, and passes through a slot292 in a peripheral region of the support base 122. An upper end portion294 of the centering finger 142 extends above the upper support surface124 of the support base 122 to releasably contact with the upper supportsurface 124 of the support base 122. A support tab 298 for supportingthe substrate 112 is positioned on the upper end portion 294 of thecentering finger 142. A substrate support notch 299 is formed at anintersection of the support tab 298 with the upper end portion 294. Alower end portion 296 of the centering finger 142 is located eccentricfrom the shaft 146. The lower end portion 296 is weighted to bias thecentering finger 142 by gravity action into a position to contact withthe upper support surface 124 of the support base 122. As shown, whenthe centering finger 142 loses contact with the opposing plate 144,which may be achieved by moving the substrate support assembly 120upward in one example of implementation, the gravity action G exerted onthe lower end portion 296 thereby causes the centering finger 142 topivot about the shaft 146, so that the upper end portion 294 movesradially inward to contact the upper support surface 124 of the supportbase 122. As further discussed in FIGS. 3A and 3B, the three or morecentering fingers 242 are evenly distributed along a periphery of thesubstrate 212 and coordinately move to support the substrate 112.

FIG. 2B is a partially enlarged cross-sectional view illustrating onecentering finger 142 in a centering position. As shown in FIG. 2B, whenthe centering finger 142 loses contact with the opposing plate 144,which may be achieved by moving the substrate support assembly 120upward in one example of implementation, the gravity action G exerted onthe lower end portion 296 thereby causes the centering finger 142 topivot about the shaft 146, so that the upper end portion 294 movesradially inward to contact and exert a displacement force F on theperipheral edge of the substrate 112 in a direction toward the referenceaxis Z. It is worth noting that the thickness of the upper end portion294 may be designed slightly higher than the top surface of thesubstrate 112. When the displacement force F is applied by the upper endportion 294, the peripheral edge of the substrate 112 can thereby beprevented from slipping over the upper end portion 294.

To release the substrate 112, FIG. 2C is a partially enlargedcross-sectional view illustrating the centering finger 142 in adisengaging position. The support base 122 may be moved downward to pushthe lower end portion 296 of the centering finger 142 into contactagainst the opposing plate 144, which counteracts the gravity actionexerted on the lower end portion 296. As a result, the centering finger142 is caused to pivot in an opposite direction so that the upper endportion 294 moves out of contact with the peripheral edge of thesubstrate 112.

As has been described above, the construction of the centering mechanism140 thus is able to automatically support the substrate 112 by using thegravity action to bias each centering finger 142. The location of thecentering fingers 142 on the substrate support assembly 120 may dependon the contour shape of the substrate to center.

FIG. 3A is a simplified overhead view of one embodiment in which threecentering fingers 142 may be used to support a circular substrate 112 ata distance from the support base 122. The three centering fingers 142are regularly spaced around a circle centered on the reference axis Z.The combination of each support tab 298 and the upper end portion 294 ofeach finger form a pocket for supporting the edge of the circularsubstrate 112. In other embodiments not shown, more centering fingersmay be positioned in different arrangements to support other substratesof different contour shapes.

FIG. 3B is a simplified overhead view of one embodiment of a centeringmechanism 140 using three centering fingers to center a substrate 112.The three centering fingers 142 are regularly spaced around a circlecentered on the reference axis Z, and each centering finger 142 is ableto apply a radial displacement force F to center the circular substrate112. In other embodiments not shown, more centering fingers may bepositioned in different arrangements to center other substrates ofdifferent contour shapes.

To effectively center the substrate 112, each centering finger 142 alsoneeds to apply a sufficient amount of displacement force F to move thesubstrate 112, which is in relation to the mass included in the weightedlower end portion 296. In one implementation, the included mass may bein a range between about 10 grams to about 500 grams. Various ways maybe implemented to include the proper mass in the lower end portion 296,such as by forming a massive lower end portion 296 of a larger size.

FIG. 4 illustrates a variant embodiment in which an embedded solidmaterial 402 of a higher mass density may be used to form the weightedlower end portion 296 of the centering finger 242. Methods to embed thesolid material 402 in the centering finger 142 may include, for example,sintering a ceramic material used for making the centering finger 142around the solid material 402. The solid material 402 may be molybdenumor other suitable materials of a mass density higher than thesurrounding material used for the centering finger 142. Inimplementations that may impose limits on the size of the weighted lowerend portion 296, the use of the embedded solid material 402 of a highermass density allows effectively increasing the mass of the weightedlower end portion 296 without increasing its size.

While the foregoing embodiments illustrate certain specific ways toimplement and operate the centering mechanism, many variations may beenvisioned. For examples, in alternate embodiments described hereafter,other constructions may be implemented for each centering finger.

FIGS. 5A-5C are partial cross-sectional views illustrating anotherembodiment of a centering finger 542. The centering finger 542 ispivotally mounted to a bracket 543, which extends out of an outerboundary of the support base 122, via a shaft 546. The support surfaceof the support base 122 may be smaller than the surface area of thesubstrate 112, so that a peripheral portion of the substrate 112 inplace on the support base 122 is free of support contact. Like theembodiments described above, the centering finger 542 includes an upperend portion 594 adapted to contact with the peripheral edge of thesubstrate 112 when the centering finger is in a centering position asshown in FIG. 5B and a support tab 598 for supporting the substrate whenthe centering finger 542 is in a supporting position as shown in FIG.5A. The centering finger 542 further includes a weighted lower endportion 596 eccentric from the shaft 546 to bias the centering finger542 into a position against the surface of the support base 122 when thecentering finger 542 is in a supporting position. The weighted lower endportion 596 also biases the centering finger 542 against the peripheraledge of the substrate 512 when the centering finger 542 is in thecentering position. In addition, the centering finger 542 includes adistal prong 590 that is opposite the lower end portion 596 relative tothe shaft 546, and is arranged below an opposing plate 544. As shown inFIG. 5A, to support the substrate 112, the lower end portion 596 of thecentering finger 542 is subject to the gravity action G that biases thecentering finger 542 and causes the upper end portion 594 to contact thesurface of the support base 122. As shown in FIG. 5B, to center thesubstrate 112, the lower end portion 596 of the centering finger 542 issubject to the gravity action G that biases the centering finger 542 andcauses the upper end portion 594 to apply the displacement force F onthe peripheral edge of the substrate 112.

As shown in FIG. 5C, to disengage the upper end portion 594 from theperipheral edge of the substrate 112 or the surface of the support base122, the substrate support assembly 120 may be moved upward so that thedistal prong 590 comes into contact with the opposing plate 544. As thesubstrate support assembly 120 moves further upward relative to theopposing plate 544, the gravity action on the lower end portion 596 isovercome and the centering finger 542 rotates about the shaft 546 todisengage the upper end portion 594 from the peripheral edge of thesubstrate 112. In one embodiment, the centering finger 542 may bereleased during processing upon centering, thus preventing undesireddeposition on the upper end portion 594, and reducing non-uniformity ofthe process due to the presence of the centering finger 542. It is worthnoting that instead of moving the substrate support assembly 120carrying the centering finger 542 relative to the opposing plate 544,alternate embodiments may design the opposing plate 544 movable relativeto the substrate support assembly 120 to contact the distal prong 590and cause the upper end portion 594 to disengage from the substrate 112.

FIG. 6 is a partial cross-sectional view illustrating another variantembodiment of a centering finger 642. Like the previous embodiments, thecentering finger 642 is pivotally mounted on the support base 122 via ashaft 646. The centering finger 642 includes an upper end portion 694and a support tab 698 adapted to support the substrate 112, and aweighted lower end portion 696 eccentric from the shaft 646 to bias thecentering finger 642 under the gravity action. However, unlike theprevious embodiments, the eccentricity of the lower end portion 696relative to the shaft 646 is configured to bias the centering finger 642into a position that disengages the upper end portion 694 from thesubstrate 112. To position the centering finger 642 in a supportingposition, an opposing plate 650 that is coupled to a servo or step motor652 and a controller 654 is controllably moved to interact with thecentering finger 642. More specifically, the opposing plate 650 movesupward to push on the lower end portion 696 and cause the centeringfinger 642 to pivot about the shaft 646 and leave the biased position.The controller 654 receives an operation signal 653 from the motor 652,and accordingly issues a control signal to the motor 652 to control theoutput of the motor 652. The controlled range of upward motion of theopposing plate 650 thereby causes a controlled displacement of the upperend portion 694 to move and support the substrate 112.

In embodiments, where the centering finger 642 is in a centeringposition, the support tab 698 contacts a peripheral edge of thesubstrate 112 and the weighted lower end portion 696 moves eccentricfrom the shaft 646 to bias the centering finger 642 under the gravityaction.

In one embodiment, the controller 654 monitors the force applied to asubstrate being centered by each centering finger 642 using theoperation signal 653. In one embodiment, the operation signal 653 may betorque of the motor 652. When the operation signal 653, e.g., torque ofthe motor 652, reaches a critical value indicating the force applied tothe substrate being centered reaches a predetermined amount, thus, thesubstrate is adequately centered. The controller 654 then stops to motor652 to avoid over centering, thus, preventing damages to the substrate.

To disengage the upper end portion 694 from substrate 112, the opposingplate 650 moves downward, which causes the centering finger 642 torecover the biased position under the gravity action applied on theweighted lower end portion 696.

FIG. 7 is a partial cross-sectional view illustrating yet anotherembodiment of a centering finger 742. The centering finger 742 is formedas a resilient member, such as an elongated ceramic spring, that has afirst end 752 fixedly mounted on a frame 748 separate from the supportbase 722, and a second end 754 extending above the support base 722through an opening 756 formed in the support base 722. The second end754 comprises a support ledge 758 for supporting the substrate 112 whenthe centering finger 742 is in a supporting position. In one embodiment,to center the substrate 112 relative to the reference axis Z, thecentering finger 742 is biased to push on the peripheral edge of thesubstrate 112 in a direction toward the reference axis Z. To disengagethe centering finger 742 from the contact with the substrate 712, anopposing actuator 760 may be controllably moved to interact with thecentering finger 742. The actuator 760 may come into contact with thecentering finger 742, and push on the centering finger 742 that therebydeflects away from its biased position to disengage from the substrate712.

Process:

Methods for centering a substrate in a processing chamber are alsoprovided. Although discussed with reference to FIGS. 2A-2C, it should beunderstood that these methods are applicable to any processing systeminvolving the heating and centering of a substrate.

In one embodiment, a substrate support assembly 120 having an embeddedheater 103 and a heated upper support surface 124 adapted to receive asubstrate 112 is provided. A plurality of centering fingers 142 disposedalong a circle centered at a reference axis “Z” substantiallyperpendicular to the upper support surface 124 is provided. Eachcentering finger 142 comprises the upper end portion 294 configured tocontact a peripheral edge of the substrate 112, and the upper endportion 294 is radially movable towards and away from the reference axis“Z”. A support tab 298 is positioned on the upper end portion 294 and asubstrate support notch 299 is formed at an intersection of the supporttab 298 and the upper end portion 294, for supporting the substrate 112at a distance “A” from the support surface 124 of the substrate supportassembly 120. In one embodiment, the distance “A” between the heatedupper support surface 124 and the substrate 112 is selected such thatthe thermal resistance between the heated upper support surface 124 andthe substrate 112 creates a different temperature on the substrate 112without changing a setpoint temperature of the embedded heater 103.

In one embodiment, the substrate 112 is positioned on the support tabs298 of each of the plurality of centering fingers 142. In oneembodiment, the combination of each support tab 298 and the upper endportion 294 of each of the plurality of centering fingers 142 form apocket for supporting the edge of the circular substrate 112 and thesubstrate 112 is positioned within the pocket.

In one embodiment, a pre-treatment process is performed on the substrate112 at a first processing temperature of the substrate 112. In oneembodiment, the pre-treatment process is an anneal process. In oneembodiment, the anneal process is performed at a substrate temperatureof between about 250° C. and about 270° C.

In one embodiment, after the pre-treatment process, the substrate 112 isremoved from the support tabs 298. The upper end portion 294 of eachcentering finger 142 is moved radially outward and away from thereference axis “Z”. The substrate 112 is placed on the substrate supportassembly 120, wherein the substrate 112 and the centering fingers 142 donot contact. The upper end portion 294 of each centering finger 142 ismoved radially inwards to contact a peripheral edge of the substrate 112for centering the substrate 112. The substrate 112 is centered using theupper end portions 294 of the centering fingers 142.

In one embodiment, after centering the substrate 112, a depositionprocess is performed on the substrate 112 at a second processingtemperature of the substrate, wherein the first processing temperatureis different from the second processing temperature. In one embodiment,the second processing temperature is between about 350° C. and about400° C.

In one embodiment, a setpoint temperature of the embedded heater 103 isthe same for both the pretreatment process and the deposition process.In one embodiment, the setpoint temperature of the embedded heater 103is the same as the temperature of the deposition process. In oneembodiment, the setpoint temperature of the embedded heater 103 isbetween about 350° C. and about 400° C.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method for centering a substrate, comprising: providing a substratesupport having an embedded heater and a support surface operable toreceive a substrate; providing a plurality of centering fingers disposedalong a circle centered at a reference axis substantially perpendicularto the support surface, each centering finger comprising: an end portionoperable to contact a peripheral edge of the substrate, and the endportion is radially movable towards and away from the reference axis; asupport tab positioned on the end portion; and a substrate support notchformed at an intersection of the support tab and the end portion, forsupporting the substrate at a distance from the support surface of thesubstrate support; positioning the substrate on the substrate supportnotch of each of the plurality of centering fingers; performing apre-treatment process on the substrate at a first processing temperatureof the substrate; removing the substrate from the support tabs; movingthe end portion of each centering finger radially outward and away fromthe reference axis; placing the substrate on the substrate support,wherein the substrate and the centering fingers do not contact; movingthe end portion of each centering finger radially inwards to contact theperipheral edge of the substrate for centering the substrate;positioning the substrate with the end portions of the centeringfingers; and performing a deposition process on the substrate at asecond processing temperature of the substrate, wherein the firstprocessing temperature is different from the second processingtemperature.
 2. The method of claim 1, wherein the distance between thesupport surface and the substrate is selected such that a thermalresistance between the support surface and the substrate create adifferent temperature on the substrate without changing a setpointtemperature of the embedded heater.
 3. The method of claim 2, whereinthe setpoint temperature of the embedded heater is the same for both thepretreatment process and the deposition process.
 4. The method of claim2, wherein the first processing temperature of the substrate is betweenabout 250° C. and about 270° C. and the second processing temperature ofthe substrate is between about 350° C. and about 400° C.
 5. The methodof claim 1, wherein moving the end portion of each centering fingercomprises pivoting each of the centering fingers about a shaft mountedon the substrate support.
 6. The method of claim 1, wherein moving theend portion of each centering finger radially inwards comprisesreleasing a weighted portion eccentrically coupled to the centeringfinger and moving the end portion of each centering finger radiallyoutwards comprises lifting the weighted portion with an opposing member.7. The method of claim 5, wherein moving the end portion of eachcentering finger radially inwards comprises pivoting the centeringfinger from a shaft using an opposing member, and moving the end portionof each centering finger radially outwards comprising releasing thecentering finger from the opposing member.
 8. The method of claim 1,wherein moving the end portion of each centering finger radially inwardscomprises: pivoting the centering finger from a shaft mounted on thesubstrate support using an opposing member, and moving the end portionof each centering finger radially outwards comprises releasing thecentering finger from the opposing member; monitoring an operationalsignal of a motor driving the opposing member, wherein the operationalsignal corresponds to a centering force applied from the centeringfinger to the substrate; and stopping the opposing member when thecentering force reaches a critical value.
 9. The method of claim 1,wherein each of the centering fingers comprises a resilient memberbiased radially towards the reference axis, and moving the end portionof each centering finger radially outwards comprises pushing theresilient member using an opposing member, and moving the end portion ofeach centering finger radially inwards comprising releasing thecentering finger from the opposing member.
 10. The method of claim 1,wherein pivoting the centering fingers comprises interacting thecentering fingers with an opposing member.
 11. An apparatus forpositioning a substrate in a processing chamber, comprising: a substratesupport having a support surface adapted to receive the substrate; aplurality of centering fingers operable to support the substrate at adistance parallel to the support surface and operable to center thesubstrate relative to a reference axis substantially perpendicular tothe support surface, wherein the plurality of centering fingers aremovably disposed along a periphery of the support surface, and each ofthe plurality of centering fingers comprises: a first end portionoperable to either contact or support a peripheral edge of thesubstrate, the first end portion comprising: an upper end portionextending above the support surface of the substrate support operable toreleasably contact the peripheral edge of the substrate; a support tabpositioned on the upper end portion; and a substrate support notchformed by an intersection of the support tab and the upper end portion,operable to support the substrate; and a lower end portion having anembedded mass of solid material weighted to bias the centering finger bygravity action into a first position to contact the support surface; anopposing member operable to interact with each of the plurality ofcentering fingers to move the first end portion; and a controlleroperable to monitor an operation signal of a motor coupled with amovable member of the opposing member, wherein the opposing member isoperable to move the first end portion of each of the plurality ofcentering fingers towards the first position, and the controller isoperable to determine an end point of centering by monitoring theoperation signal of the motor.
 12. The apparatus of claim 11, whereinthe substrate support encapsulates at least one embedded heater operableto controllably heat the substrate support and the substrate positionedthereon to a predetermined temperature.
 13. The apparatus of claim 11,further comprising a circumscribing shadow frame positioned to preventdeposition on the peripheral edge of the substrate, the substratesupport, and the plurality of centering fingers operable to reduceflaking and particle contamination in the processing chamber.
 14. Theapparatus of claim 11, further comprising: a fiber optic temperaturesensor operable to provide a metric indicative of a temperature profileof a backside of the substrate, wherein the fiber optic temperaturesensor is positioned in the substrate support.
 15. The apparatus ofclaim 11, further comprising: one or more purge gas inlets coupled witha purge gas source operable to supply purge gas to a backside of thesubstrate for preventing particle contamination caused by deposition onthe backside of the substrate when the substrate is supported by theplurality of centering fingers, wherein the one or more purge gas inletsare positioned in the substrate support.
 16. The apparatus of claim 11,wherein the opposing member is operable to move the first end portion ofeach of the plurality of centering fingers towards the second position,and each of the plurality of centering fingers is independently biasedtowards the first position, and a combination of biasing forces from theplurality of centering fingers centers the substrate relative to thereference axis.
 17. The apparatus of claim 11, wherein each of theplurality of centering fingers is made of a material including ceramic,aluminum nitride, aluminum oxide, aluminum, or combinations thereof. 18.The apparatus of claim 11, wherein the lower end portion is eccentricfrom a shaft, which pivotally mounts the centering finger to thesubstrate support, wherein the first end portion and the lower endportion are disposed on opposing sides of the shaft.
 19. The apparatusof claim 11, wherein the plurality of centering fingers are operable toperform a centering sequence including a backward movement of the firstend portion from the first position to a second position and a forwardmovement of the first end portion from the second position to the firstposition.
 20. The apparatus of claim 19, wherein the backward movementcauses the centering finger to release the peripheral edge of thesubstrate, the release causing the substrate to rest on the supportsurface, and the forward movement causes the centering finger to pushthe substrate placed on the support surface in a direction toward thereference axis to position the substrate.